[Applications of optical topography in neurosurgery].

Optical topography is a new alternative for noninvasive functional brain mapping. It uses near infrared light projected from the scalp into the brain. The reflected light which is sampled 30 mm apart from the injection probe carries the information of hemoglobin concentration change of the regional brain tissue lying at the midpoint of probes. When mapped using 24 channels, we see the real time brain activities during various tasks allowing the head movements as well. It is utilized in measuring the language function, and diagnosis of epilepsy focus. Several such clinical applications are demonstrated. The brain activities are measured during finger tapping. The mapping during word generation task shows the activities of Broca's area indicating the hemispheric dominancy of language function. We correlated the results between optical topography measurement and amytal test, showing 85% matching according to the language dominancy. It also useful in identifying the epilepsy focus because the hemoglobin increases at the focus region in the initial phase of epileptic seizures. In our study, the feasibility of optical topography in focus diagnosis is confirmed in 85% of 27 cases. The advantages of optical topography are as follows. 1: It is portable to various clinical scenes including patient ward and outpatient clinic. 2: It can be used conjunction with fMRI and MEG. 3: It measures the brain activities even during the head movements.